1. Field of the Invention:
The present invention relates generally to the field of environmental protection mechanisms and procedures. More specifically the present invention relates to a secondary containment cap apparatus for sealingly securing over a turret or other critical portion of a hazardous gas primary container, to provide the container with a shield against leakage into the natural environment. Such primary containers may be free-standing or vehicle-mounted. The hazardous gas within the primary container is a gas which is poisonous, caustic or otherwise health threatening, such as chlorine and sulphur dioxide liquified gas.
For each type of primary container, the secondary containment cap apparatus fits to an exterior surface of the primary container and retains any gas leaking from the primary vehicle into the interior of the apparatus to prevent escape into the environment. The secondary containment cap apparatus in its essential form includes a substantially cup- or bubble-shaped cap wall defining a concave cap interior and a cap abutment port surrounded by a cap port rim shaped to follow and fit sealingly against a region of the primary container exterior surface to enclose this region, means for controlled release of gas within the cap wall into secure containers or scrubber means, and attachment means for securing the apparatus to the primary container with the port rim sealingly fitted against the primary container exterior surface.
2. Description of the Prior Art:
In recent years there have been numerous instances of chlorine gas released from bulk storage tanks, railroad tanker cars, tanker trucks and barges. Many communities have adopted new regulations requiring containment of toxic gas releases, such as Article 80 of the Uniform Fire Code and the Toxic Gas Ordinance. A problem with existing chlorine tanks and valves has been that they have no secondary containment, so that a release of chlorine from the tank or tank valving causes an instant and life threatening discharge of chlorine gas.
There have in recent years been devices intended for containing and scrubbing chlorine gas leaking from cylinders, and vehicles. These devices traditionally have included a hood or building structure placed around the leaking cylinder or vehicle and a scrubber apparatus for gradually removing the chlorine gas from the air within the hood or building. A problem with these devices has been that the containment buildings and hoods are not capable of withstanding the pressure and corrosive nature of suddenly released quantities of chlorine gas. Being largely intended for ton and 150 pound chlorine gas cylinders, such technology is wholly ineffective and unsuited for the large, perhaps 275 ton tanks found on chlorine transport vehicles and the sometimes massive stationary bulk storage tanks.
A solution to the problem of safely draining leaking chlorine cylinders has been found and is disclosed in U.S. Pat. No. 5,607,384 and 5,819,787, issued on Mar. 4, 1997 and Dec. 13, 1998, respectively, to the present applicant. These patents disclose sealing leaking chlorine cylinders in a pressure-withstanding secondary containment vessel, resembling on some ways an iron lung. Gas is slowly released through a valve in the secondary containment vessel to a scrubber apparatus of conventional design at a suitable metered rate. In the event of a catastrophic rupture and sudden release of gas from the cylinder, the secondary containment vessel entirely and safely contains the released gas, which once again is discharged at a suitable rate to a scrubber apparatus or put into process. A limitation to this approach is that it is impractical to build secondary containment vessels of the type disclosed in these patents which are large enough to receive bulk storage tanks and chlorine transport vehicles, and it is impractical to attempt to move such a leaking storage tank or tanker vehicle to the site of such a massive vessel or to move the massive vessel to and around the tanker vehicle. Additionally, there are so many sizes and shapes of tanks and transport vehicles that no single size and shape of receiving vessel could be suitable for all of them. Further a hood or alternative method may not fully comply with fire codes.
It is thus an object of the present invention to provide a secondary containment cap apparatus for enclosing a critical portion of a primary container such as a hazardous fluid containment bulk storage or vehicle tank, which is manufactured separately from the primary container, so that any fluid subsequently leaking from that critical portion of the primary container is contained within the containment cap apparatus and can be drained off through a port and valve in the apparatus into cylinders or other receiving means in the conventional way for ordinary usage. As a result, there is no need to go to the considerable expense of scrubbing the leaking fluid and no need to expose anyone to the dangers involved in such a clean-up operation.
It is more specifically an object of the present invention to provide such a cap apparatus which encloses the gas release port and valve of a primary container in such a limited secondary containment structure which is less expensive than providing secondary containment of the entire primary container.
It is an additional object of the present invention to provide such a cap apparatus in which the secondary containment cap is capable of withstanding the maximum hazardous fluid pressure which can be exerted by the quantity of retained hazardous fluid so that the natural environment is safely shielded from the hazardous fluid, and in which the primary container gas release port is fitted with a remote operating container valve which is operable from outside the containment cap apparatus so that the valve can be operated without entering the containment cap apparatus and no personnel are therefore exposed to leaking hazardous fluid.
It is a further object of the present invention to provide such a cap apparatus which is equipped with a hazardous fluid pressure/vacuum gauge and detection devices for indicating leaks and optionally for indicating completed draining of hazardous fluid from the cap structure.
It is still another object of the present invention to provide such a cap apparatus which complies with Article 80 of the Uniform Fire Code and with the California Toxic Gas Ordinance.
It is yet another object of the present invention to provide such a cap apparatus which has a fail-safe valve connected to its release fitting, the fail-safe valve being electrically wired to a motion and impact sensor, and connected to a hazardous fluid leakage sensor, which rapidly closes the fail-safe valve in the event of an earthquake, an attempt to move the primary container, or a hazardous fluid leak, and such a cap apparatus which has an on-board alarm system, with backup emergency power.
It is finally an object of the present invention to provide such a cap apparatus which is highly reliable and can be manufactured at an expense relatively comparable to that of existing containment systems.